Downgade BIOS Toshiba Portege z30-a

[Fern]

How to downgrade the bios on laptop? Possible to recovery via crisis usb flash drive?
Toshiba Portege z30-a (PT241U-0ER012) link to the official website https://support.dynabook.com/support/mod...Id=3333785
platform id: FAUXSY4 A3805A

Before to the update bios, version was:
BIOS 4.0
EС 1.0
After the update:
BIOS 4.3
EС 1.6
After updating the BIOS, the laptop is turn on for a very long time...
EC is BGA IT6511FN. I have only TL866II plus.

AIDA64:
Type BIOS: Toshiba UEFI
Company name: Toshiba America information systems, Inc.
BIOS is AMI?

I downloaded the BIOS file version 4.0 from the official website Toshiba and decrypted it.
And got a file size of about 3.67MB, ie it's just the BIOS region. Without ME region. Attach file out4.0.zip.
I opened this file with PhoenixTool 2.73. He smashed it into modules.
I am interested in the contents of the module 3D17205B-4C49-47E2-8157-864CD3D80DBD_1777.ROM.
Opened in the hex editor, at the bottom there is interesting information:

fvmain.fv
EL TORITO SPECIFICATION CD001

and this decryption bios file has lines about the EC file. looks like this(UTF-16):
ECB7????.BIN

in the bios file that i am downloaded from the website Toshiba, there is an t241v400.iso image.
This *.iso image has a file TOSHBIOS.IMG.
I am boot this *.img file from a flash drive via grud4dos, but got an error:
the bios and/or ec/kbc is not compatible

how to solve the problem with a long turn on the laptop?